Conservation Minister Nick Smith has admitted there could have been sightings of Maui’s Dolphins in areas opened for oil and gas exploration, but denies he misled Parliament.

Smith last week said not a single Maui's Dolphin had been sighted inside an area opened up by the Government for oil drilling as part of its 2014 Block Offer, which includes more than 3000 sq km of the West Coast North Island Marine Mammal Sanctuary.

But Green Party co-leader Russel Norman said Department of Conservation figures showed there had been 10 sightings in the area.

“This gives us no confidence that this Government is taking the plight of the Maui’s Dolphin seriously,” he said.

Norman said that while the International Whaling Commission was calling for greater protections, the speculating was putting them at greater risk.

Smith this evening confirmed what he described as some unverified sightings in the newly-opened area which were brought to his attention today.

He conceded he should have been more clear in the House but did not accept that he had misled Parliament.

“When I made the statement that there was not a single observation of the Maui’s Dolphin I was referring to the independent programme that the Government had set up as part of the Maui’s Dolphin risk management plan.”

Smith said this involved 809 days of observations where not a single Maui’s Dolphin was seen in the area, and maintained their presence was “close to zero”.

The petroleum industry posed a very low risk to the safety of the dolphin - the world's most endangered dolphin with a population of just 55, all residing in New Zealand waters off the west coast of the North Island, he said.

"All the technical advice on the Maui's Dolphin is that over 95 percent of the risk is from set netting and from fishing," he said.

Prime Minister John Key also dismissed the Green Party claims that the permits put the dolphins at greater risk as “based on a load of mumbo jumbo”.

“What a load of nonsense. If that was absolutely correct then given that we’ve been drilling the Taranaki region since the 1960s and there’s never been a situation where a Maui Dolphin has been killed as a result of that - you think it would have happened some time in the last 50 years. It’s just the mumbo jumbo that the Greens go on about.”